This invention relates to apparatus for transferring fluid from pressurized containers and more particularly to can-tapping fluid control valve apparatus.
Although not limited to use with air-conditioning systems, the present invention is particularly useful in recharging such systems. Air-conditioning systems for vehicles or buildings generally employ a compressible working fluid or refrigerant. While such systems are generally well sealed, some of the refrigerant is inevitably lost and must be replaced. If major repairs of the system are required, the entire refrigerant charge may have to be replaced. The commonly used refrigerants are conveniently packaged in small disposable containers or cans holding, for example, one pound each. Instead of having an integral outlet valve, these cans typically have a pierceable top seal which may be pierced by some type of tapping mechanism to gain access to the can and allow the fluid to be conducted by a hose to an air-conditioning system inlet.
The tapping mechanism is typically part of a control valve and safety valve arrangement. A control valve is needed to provide controlled flow of the pressurized fluid from the can. One way valve means are normally employed to prevent accidental flow of pressurized fluid back into the can. Such flow into the can would raise the internal pressure level and would cause the can to explode. For similar reasons, a safety valve is sometimes employed to vent fluid when excessive pressure is encountered.
References known to the applicant which may be relevant to the invention include U.S. Pat. No. 3,817,302 issued to Kowal et al in June of 1974, U.S. Pat. No. 2,536,836, issued to Bowling on Jan. 2, 1951, U.S. Pat. No. 1,275,783 issued to Steinmetz on Aug. 13, 1918, U.S. Pat. No. 2,865,410 issued to Neely on Dec. 23, 1958, and U.S. Pat. No. 3,509,905 issued to Mullins on May 5, 1970.
The Kowal Patent discloses a can tapping valve apparatus using separate elements for controlling the fluid flow, for stopping the reverse flow and for regulating pressure. This apparatus taught by Kowal is complicated and requires a number of separate parts, each performing an individual function. In particular, a flow control valve, a check valve and pressure regulating elements operate independently.
The Steinmetz and Bowling Patents each teach generally the use of a spherical ball in a fluid flow control valve. Neither of these devices is particularly adaptable for use as a can tapping valve as in the present invention. The Bowling device, for example, is relatively complicated and requires considerable machining to manufacture and thus would be a relatively expensive flow control valve.
The Neely and Mullins Patents teach apparatus for providing access to a container or pipe having some form of piercing point and a valve. Each employ an air valve core of the type employed in automotive tire valves. Such devices are not believed to be adaptable for use as a can tapping valve according to the present invention.
The can tapping valve of the present invention has particularly applicability as a consumer unit to be used in adding refrigerant fluid to refrigeration systems, particularly, automotive or residential air-conditioning systems. Such applications require inexpensive and uncomplicated devices, and prior art systems have not satisfied the demand.
For such use it is desirable, as taught by Kowal, that some pressure relief means be provided to avoid excessive pressure conditions in case the flow control valve has been connected to a high pressure source of fluid instead of a low pressure source. While some prior art systems have provided for pressure relief, a simpler and less expensive means has been needed.